How can I extend the wires of my soil moisture sensor without dropping voltage?

My control box is 15 meters from the plants. I also have my 5v power supply for my sensor. I have 2 sensors.

Specification for control box:

Power supply: 3.3v or 5v
Output voltage signal: 0~4.2v Current: 35mA

Pin definition:
Analog output (Blue wire)
GND (Black wire)
Power (Red wire)

  • 1
    "my controller is not a arduino but a PLC" - so what? your controller isn't relevant to the question... Commented Nov 25, 2016 at 2:02

2 Answers 2


If you need to reduce the voltage drop over a given distance, you need to increase the size of wiring being used.

In this case, with a load of 35mA and a distance of 15m, the voltage drop using 16-18ga wire would be negligible. As in less than a half percent.

Here is a voltage drop calculator that you may find useful:

Voltage Drop Calculator

  • thank you for your help sir, but can it be possible to have to voltage drop until the end of the wire? what would be the solution, thank you
    – user63021
    Commented Nov 25, 2016 at 6:34
  • 1
    @JNV05 I don't understand what you're saying, and I don't think you do either. I suggest you do more research, then post a separate question. Commented Nov 25, 2016 at 11:33

Voltage drop occurs due to a resistance or load in the circuit. Using Connor's supplied calculator will tell you the amount your source voltage will be reduced by the cable run to your sensor. There will be a further drop due to the resistance of, and impedance created by, your sensor. This will most likely be negligible.

Most PLCs will have a reasonable amount of tolerance for voltage levels if you're using it on a digital channel.

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